Recently, as telephone sets in which a plurality of handset units can additionally be installed are made available, a growing number of users have come to buy a handset unit separately after the purchase of a telephone set for additional installation. In order to install an additional handset unit, there is a need to perform an extension process on a base unit and the handset unit. The extension process involves a step to register an identification code for identifying the base unit (hereafter referred to as “ID (Identification”) with the handset unit which is an afterward purchase, and a step to register the addition of the handset unit with the base unit.
To be more specific, the base unit and the handset unit of the telephone set are each provided with an extension mode, namely an operational mode designed specifically for installation of an additional handset unit. In order for the handset unit to be additionally installed in the base unit, it is necessary to bring both of the base unit and the handset unit into the extension mode by performing specific operations on the base unit and the handset unit. Following the establishment of the extension mode, a handset unit number for handset unit identification is inputted to the base unit to indicate the how-manieth handset unit to be additionally installed it is. Then, the base unit transmits the ID stored therein, the handset unit number inputted thereto, and a signal for indicating an instruction of additional installation to the handset unit wirelessly by means of a setting channel. Upon the receipt of the signals, the handset unit writes the ID and the handset unit number indicated by the signals received into memory means.
The handset unit transmits a signal for notifying the reception of the signal indicating an instruction of additional installation to the base unit by means of a setting channel. Upon the receipt of this signal, the base unit judges that the additional installation has been completed properly, and writes the addition of the handset unit into the memory means. In this way, the handset unit having stored therein the ID and the handset unit number can be wirelessly connected to the base unit from that time forward. Moreover, in a case where the handset unit will not be used any longer because of, for example, occurrence of malfunction in the handset unit additionally installed, there arises a need to cancel the data about the handset unit stored in the base unit. In order to cancel the handset unit data, it is necessary to perform operations for bringing the base unit and the handset unit into a cancel mode to erase the data about the handset unit which is no longer used.
For example, in Japanese Unexamined Patent Publication JP-A 1-218223 (1989) is disclosed a wireless telephone system composed of a base unit and a wireless terminal. In this wireless telephone system, in accompaniment with start-up of outgoing/incoming calling actions, transmission and reception of identification data for identifying the wireless telephone system are accomplished over a control channel, and, when agreement in identification data is observed, a shift toward phone-conversation channel connection control is effected. The setting of the identification data is carried out as follows. The base unit sends out identification data set for the base unit, as well as checking data inputted to the base unit, to the wireless terminal. When there is agreement between the checking data received by the wireless terminal and checking data inputted to the wireless terminal, the wireless terminal sets the received identification data in the rewritable memory of the wireless terminal. In this case, by setting the identification data in advance in the read-only memory of the base unit, it is possible to set the identification data in the rewritable memory of the wireless terminal simply by inputting the checking data. This eliminates the need to set the identification data in a handset unit manually.
For example, in Japanese Unexamined Patent Publication JP-A 8-223282 (1996) is disclosed a cordless telephone set in which an additional handset unit can be installed while a telephone call is in progress between its base unit and a service center. In this cordless telephone set, handset unit data for handset unit determination is set in the memory means of the base unit and in the memory means of the handset unit under the state where the base unit is catching a telephone line or during a telephone conversation over a telephone line. A user makes a phone call to the service center so that the additional handset unit can be installed properly with the help of an explanation given by a person in charge. Therefore, even if the user is unskilled in such an installation operation, additional installation of the handset unit can be completed with ease.
For example, in Japanese Unexamined Patent Publication JP-A 2004-120208 is disclosed a telephone apparatus which employs a plurality of control channels. In this telephone apparatus, after its base unit transmits a registration command to a handset unit for the purpose of registering the handset unit, if no response command to the registration command is issued from the handset unit, the base unit makes a second attempt to transmit the registration command following the changing of the control channel for registration command transmission. That is, even if the initial control channel for registration command transmission is different from the corresponding one of the handset unit, the base unit transmits the registration command following the completion of control channel changing. This obviates the necessity for the user to recognize the setting status of the control channel, and thus avoids the necessity for changing the control channel manually.
Additional installation or cancellation of a handset unit cannot be achieved without performing particular manual operations. Especially, in order to establish an extension mode or a cancel mode which is provided to prevent erroneous additional installation or cancellation, more often than not, complicated operations are required. Therefore, many users tend to make mistakes with operations related to additional installation or cancellation.
Furthermore, in carrying out additional installation, communications between a base unit and a handset unit are established by means of radio waves. In this case, the additional installation could end in failure for the following reasons: the base unit or the handset unit suffers from a trouble occurring in its radio wave control section; the frequency of radio waves employed in the additional installation is being in use by another telephone; or the conditions of radio waves become unstable due to occurrence of noise or the like. Thus, a failure in the extension process could occur for a variety of reasons including misoperation, telephone malfunction, radio wave conflict with another telephone, and radio wave conditions.
According to the art disclosed in JP-A 1-218223, identification data is set in advance in the read-only memory of the base unit. By doing so, the identification data can automatically be set in the rewritable memory of the wireless terminal. In this case, although misoperation associated with the setting of the identification data can be prevented, there is still a possibility of extension process failure due to other causes. According to the art disclosed in JP-A 2004-120208, by effecting the changing of the control channel for transmitting a registration command, it is possible to eliminate the need for manual operations required to resolve a control channel mismatch. However, there is still a possibility of extension process failure due to other causes. In these prior art practices, in the event of an extension process failure, the extension process is carried out once again with reference to an operating guide borne in an instruction manual or an operating guide displayed on the display screen of the base unit of the telephone set, for instance. However, in the case of referring to the operating guide borne in an instruction manual or the operating guide displayed on the display screen of the base unit of the telephone set or the like, much time and effort need to be taken to find out the description of a target operation. This gives rise to a problem that a retry of the extension process cannot be started immediately.
According to the art disclosed in JP-A 8-223282, even if an extension process failure occurs, it is possible to achieve the extension process with the help of an explanation given by a person in charge in the service center. In this case, there is no need for finding out the description of a target operation in the operating guide. However, even if the user makes a phone call to the service center to ask for an explanation given by a person in charge in the service center, it could be impossible to get through thereto due to line congestion. This gives rise to a problem that a retry of the extension process cannot be started immediately.